Development and analysis of decorrelation filters for binaural rendering of Audio Definition Model content

This paper presents the development and analysis of decorrelation filters for use in the binaural EBU ADM renderer (BEAR). The BEAR renders binaural audio from ADM-defined input using a virtual loudspeaker array. Decorrelation filters are used to improve the perception of audio source extent, and play an important part in the rendering of spatial audio. Several preexisting decorrelation techniques are described, and the novel phase-controlled noise filter is presented. The phase-controlled noise is parametrized to provide a flexible trade-off between decorrelation performance and temporal smearing.A listening experiment was used to investigate the perception of timbral and spatial characteristics of differently decorrelated audio sources. Seven candidate filter sets were included in the evaluation, which used the BEAR system to generate stimuli. Results showed that an exponentially-decaying white noise filter introduced the least colouration while also giving increased width over the reference at the frontal source position. The phase-controlled noise filter was shown to have comparable performance to alternative designs, but did not reduce colouration as desired. The perceived source width of the “point-source” reference was already quite wide and not all decorrelation filters provided significant increases in width at the frontal source position. At the lateral source position, no filters led to an increase in width over the reference, and sources were perceived to be narrower generally, with a corresponding increase in perceived distance. Future work could investigate the parameter space of decorrelation filter design in more detail with auditory modelling and an improved listening experiment method could be explored.